Influenza virus remains a major public health concern for the USA and the world. To best insure that a pandemic like the 1918-1919 episode does not reoccur, national and international surveillance, effective vaccine and novel and effective antiviral therapy are required. Here we propose a multi-institute cooperative research project focused on discovery and use of novel chemicals that selectively manipulate the immunologic response in the lung as a therapeutic approach to better control influenza viral infection. We and others have evidence in animal models that the immune response (immunopathology) to influenza contributes significantly to morbidity and mortality. We have preliminary but impressive data that low doses of sphingosine analogs administered as a single dose intratracheally but not systemically acts locally in the lung to specifically suppress antiviral T cell proliferative responses. We propose that: 1) single aerosol exposure of the lungs to a sphingosine analog will inhibit antiviral proliferation thus modulating the resultant immunopathologic injury;2) this mechanism will synergize with classic antiviral protective therapy;3) combination of these therapeutic approaches will protect the host during H5N1 infection. To test this proposal Hugh Rosen, with expertise in immunology, medicinal chemistry and human therapeutics, will continue the development of sphingosine compounds and their testing with Michael Oldstone, experienced in viral-immunobiology and use of the WSN recombinant virus expressing immunodominant CDS and CD4 T cell epitopes of LCMV. WSN recombinant infection is preceded with transfer of GFP, RFP or Th1.1 congenically labeled CD4 and CDS T cells to these LCMV epitopes allowing quantitation of flu-specific T cells in the lung. The LCMV recombinant as well as GFP-labeled WSN virus used has been prepared by the third partner in this enterprise, Yoshihiro Kawaoka, an expert in influenza viruses. Kawaoka will test novel sphingosine analogs against H5N1 influenza virus.